As We May Think

by Vannevar Bush

As Director of the Office of Scientific Research and Development, Dr.
Vannevar Bush has coördinated the activities of some six thousand leading
American scientists in the application of science to warfare. In this
significant article he holds up an incentive for scientists when the
fighting has ceased. He urges that men of science should then turn to the
massive task of making more accessible our bewildering store of knowledge.
For years inventions have extended man's physical powers rather than the
powers of his mind. Trip hammers that multiply the fists, microscopes that
sharpen the eye, and engines of destruction and detection are new results,
but not the end results, of modern science. Now, says Dr. Bush, instruments
are at hand which, if properly developed, will give man access to and
command over the inherited knowledge of the ages. The perfection of these
pacific instruments should be the first objective of our scientists as they
emerge from their war work. Like Emerson's famous address of 1837 on "The
American Scholar," this paper by Dr. Bush calls for a new relationship
between thinking man and the sum of our knowledge.
- The Editor

This has not been a scientist's war; it has been a war in which all have had
a part. The scientists, burying their old professional competition in the
demand of a common cause, have shared greatly and learned much. It has been
exhilarating to work in effective partnership. Now, for many, this appears
to be approaching an end. What are the scientists to do next?

For the biologists, and particularly for the medical scientists, there can
be little indecision, for their war has hardly required them to leave the
old paths. Many indeed have been able to carry on their war research in
their familiar peacetime laboratories. Their objectives remain much the
same.

It is the physicists who have been thrown most violently off stride, who
have left academic pursuits for the making of strange destructive gadgets,
who have had to devise new methods for their unanticipated assignments. They
have done their part on the devices that made it possible to turn back the
enemy, have worked in combined effort with the physicists of our allies.
They have felt within themselves the stir of achievement. They have been
part of a great team. Now, as peace approaches, one asks where they will
find objectives worthy of their best.

1

Of what lasting benefit has been man's use of science and of the new
instruments which his research brought into existence? First, they have
increased his control of his material environment. They have improved his
food, his clothing, his shelter; they have increased his security and
released him partly from the bondage of bare existence. They have given him
increased knowledge of his own biological processes so that he has had a
progressive freedom from disease and an increased span of life. They are
illuminating the interactions of his physiological and psychological
functions, giving the promise of an improved mental health.

Science has provided the swiftest communication between individuals; it has
provided a record of ideas and has enabled man to manipulate and to make
extracts from that record so that knowledge evolves and endures throughout
the life of a race rather than that of an individual.

There is a growing mountain of research. But there is increased evidence
that we are being bogged down today as specialization extends. The
investigator is staggered by the findings and conclusions of thousands of
other workers -- conclusions which he cannot find time to grasp, much less
to remember, as they appear. Yet specialization becomes increasingly
necessary for progress, and the effort to bridge between disciplines is
correspondingly superficial.

Professionally our methods of transmitting and reviewing the results of
research are generations old and by now are totally inadequate for their
purpose. If the aggregate time spent in writing scholarly works and in
reading them could be evaluated, the ratio between these amounts of time
might well be startling. Those who conscientiously attempt to keep abreast
of current thought, even in restricted fields, by close and continuous
reading might well shy away from an examination calculated to show how much
of the previous month's efforts could be produced on call. Mendel's concept
of the laws of genetics was lost to the world for a generation because his
publication did not reach the few who were capable of grasping and extending
it; and this sort of catastrophe is undoubtedly being repeated all about us,
as truly significant attainments become lost in the mass of the
inconsequential.

The difficulty seems to be, not so much that we publish unduly in view of
the extent and variety of present day interests, but rather that publication
has been extended far beyond our present ability to make real use of the
record. The summation of human experience is being expanded at a prodigious
rate, and the means we use for threading through the consequent maze to the
momentarily important item is the same as was used in the days of
square-rigged ships.

But there are signs of a change as new and powerful instrumentalities come
into use. Photocells capable of seeing things in a physical sense, advanced
photography which can record what is seen or even what is not, thermionic
tubes capable of controlling potent forces under the guidance of less power
than a mosquito uses to vibrate his wings, cathode ray tubes rendering
visible an occurrence so brief that by comparison a microsecond is a long
time, relay combinations which will carry out involved sequences of
movements more reliably than any human operator and thousands of times as
fast -- there are plenty of mechanical aids with which to effect a
transformation in scientific records.

Two centuries ago Leibnitz invented a calculating machine which embodied
most of the essential features of recent keyboard devices, but it could not
then come into use. The economics of the situation were against it: the
labor involved in constructing it, before the days of mass production,
exceeded the labor to be saved by its use, since all it could accomplish
could be duplicated by sufficient use of pencil and paper. Moreover, it
would have been subject to frequent breakdown, so that it could not have
been depended upon; for at that time and long after, complexity and
unreliability were synonymous.

Babbage, even with remarkably generous support for his time, could not
produce his great arithmetical machine. His idea was sound enough, but
construction and maintenance costs were then too heavy. Had a Pharaoh been
given detailed and explicit designs of an automobile, and had he understood
them completely, it would have taxed the resources of his kingdom to have
fashioned the thousands of parts for a single car, and that car would have
broken down on the first trip to Giza.

Machines with interchangeable parts can now be constructed with great
economy of effort. In spite of much complexity, they perform reliably.
Witness the humble typewriter, or the movie camera, or the automobile.
Electrical contacts have ceased to stick when thoroughly understood. Note
the automatic telephone exchange, which has hundreds of thousands of such
contacts, and yet is reliable. A spider web of metal, sealed in a thin glass
container, a wire heated to brilliant glow, in short, the thermionic tube of
radio sets, is made by the hundred million, tossed about in packages,
plugged into sockets -- and it works! Its gossamer parts, the precise
location and alignment involved in its construction, would have occupied a
master craftsman of the guild for months; now it is built for thirty cents.
The world has arrived at an age of cheap complex devices of great
reliability; and something is bound to come of it.

2

A record if it is to be useful to science, must be continuously extended,
it must be stored, and above all it must be consulted. Today we make the
record conventionally by writing and photography, followed by printing; but
we also record on film, on wax disks, and on magnetic wires. Even if utterly
new recording procedures do not appear, these present ones are certainly in
the process of modification and extension.

Certainly progress in photography is not going to stop. Faster material
and lenses, more automatic cameras, finer-grained sensitive compounds to
allow an extension of the minicamera idea, are all imminent. Let us project
this trend ahead to a logical, if not inevitable, outcome. The camera hound
of the future wears on his forehead a lump a little larger than a walnut. It
takes pictures 3 millimeters square, later to be projected or enlarged,
which after all involves only a factor of 10 beyond present practice. The
lens is of universal focus, down to any distance accommodated by the unaided
eye, simply because it is of short focal length. There is a built-in
photocell on the walnut such as we now have on at least one camera, which
automatically adjusts exposure for a wide range of illumination. There is
film in the walnut for a hundred exposures, and the spring for operating its
shutter and shifting its film is wound once for all when the film clip is
inserted. It produces its result in full color. It may well be stereoscopic,
and record with two spaced glass eyes, for striking improvements in
stereoscopic technique are just around the corner.

The cord which trips its shutter may reach down a man's sleeve within easy
reach of his fingers. A quick squeeze, and the picture is taken. On a pair
of ordinary glasses is a square of fine lines near the top of one lens,
where it is out of the way of ordinary vision. When an object appears in
that square, it is lined up for its picture. As the scientist of the future
moves about the laboratory or the field, every time he looks at something
worthy of the record, he trips the shutter and in it goes, without even an
audible click. Is this all fantastic? The only fantastic thing about it is
the idea of making as many pictures as would result from its use.

Will there be dry photography? It is already here in two forms. When Brady
made his Civil War pictures, the plate had to be wet at the time of
exposure. Now it has to be wet during development instead. In the future
perhaps it need not be wetted at all. There have long been films impregnated
with diazo dyes which form a picture without development, so that it is
already there as soon as the camera has been operated. An exposure to
ammonia gas destroys the unexposed dye, and the picture can then be taken
out into the light and examined. The process is now slow, but someone may
speed it up, and it has no grain difficulties such as now keep photographic
researchers busy. Often it would be advantageous to be able to snap the
camera and to look at the picture immediately.

Another process now in use is also slow, and more or less clumsy. For
fifty years impregnated papers have been used which turn dark at every point
where an electrical contact touches them, by reason of the chemical change
thus produced in an iodine compound included in the paper. They have been
used to make records, for a pointer moving across them can leave a trail
behind. If the electrical potential on the pointer is varied as it moves,
the line becomes light or dark in accordance with the potential.

This scheme is now used in facsimile transmission. The pointer draws a set
of closely spaced lines across the paper one after another. As it moves, its
potential is varied in accordance with a varying current received over wires
from a distant station, where these variations are produced by a photocell
which is similarly scanning a picture. At every instant the darkness of the
line being drawn is made equal to the darkness of the point on the picture
being observed by the photocell. Thus, when the whole picture has been
covered, a replica appears at the receiving end.

A scene itself can be just as well looked over line by line by the
photocell in this way as can a photograph of the scene. This whole apparatus
constitutes a camera, with the added feature, which can be dispensed with if
desired, of making its picture at a distance. It is slow, and the picture is
poor in detail. Still, it does give another process of dry photography, in
which the picture is finished as soon as it is taken.

It would be a brave man who would predict that such a process will always
remain clumsy, slow, and faulty in detail. Television equipment today
transmits sixteen reasonably good pictures a second, and it involves only
two essential differences from the process described above. For one, the
record is made by a moving beam of electrons rather than a moving pointer,
for the reason that an electron beam can sweep across the picture very
rapidly indeed. The other difference involves merely the use of a screen
which glows momentarily when the electrons hit, rather than a chemically
treated paper or film which is permanently altered. This speed is necessary
in television, for motion pictures rather than stills are the object.

Use chemically treated film in place of the glowing screen, allow the
apparatus to transmit one picture only rather than a succession, and a rapid
camera for dry photography results. The treated film needs to be far faster
in action than present examples, but it probably could be. More serious is
the objection that this scheme would involve putting the film inside a
vacuum chamber, for electron beams behave normally only in such a rarefied
environment. This difficulty could be avoided by allowing the electron beam
to play on one side of a partition, and by pressing the film against the
other side, if this partition were such as to allow the electrons to go
through perpendicular to its surface, and to prevent them from spreading out
sideways. Such partitions, in crude form, could certainly be constructed,
and they will hardly hold up the general development.

Like dry photography, microphotography still has a long way to go. The
basic scheme of reducing the size of the record, and examining it by
projection rather than directly, has possibilities too great to be ignored.
The combination of optical projection and photographic reduction is already
producing some results in microfilm for scholarly purposes, and the
potentialities are highly suggestive. Today, with microfilm, reductions by a
linear factor of 20 can be employed and still produce full clarity when the
material is re-enlarged for examination. The limits are set by the
graininess of the film, the excellence of the optical system, and the
efficiency of the light sources employed. All of these are rapidly
improving.

Assume a linear ratio of 100 for future use. Consider film of the same
thickness as paper, although thinner film will certainly be usable. Even
under these conditions there would be a total factor of 10,000 between the
bulk of the ordinary record on books, and its microfilm replica. The
Encyclopędia Britannica could be reduced to the volume of a matchbox. A
library of a million volumes could be compressed into one end of a desk. If
the human race has produced since the invention of movable type a total
record, in the form of magazines, newspapers, books, tracts, advertising
blurbs, correspondence, having a volume corresponding to a billion books,
the whole affair, assembled and compressed, could be lugged off in a moving
van. Mere compression, of course, is not enough; one needs not only to make
and store a record but also be able to consult it, and this aspect of the
matter comes later. Even the modern great library is not generally
consulted; it is nibbled at by a few.

Compression is important, however, when it comes to costs. The material
for the microfilm Britannica would cost a nickel, and it could be mailed
anywhere for a cent. What would it cost to print a million copies? To print
a sheet of newspaper, in a large edition, costs a small fraction of a cent.
The entire material of the Britannica in reduced microfilm form would go on
a sheet eight and one-half by eleven inches. Once it is available, with the
photographic reproduction methods of the future, duplicates in large
quantities could probably be turned out for a cent apiece beyond the cost of
materials. The preparation of the original copy? That introduces the next
aspect of the subject.

3

To make the record, we now push a pencil or tap a typewriter. Then comes
the process of digestion and correction, followed by an intricate process of
typesetting, printing, and distribution. To consider the first stage of the
procedure, will the author of the future cease writing by hand or typewriter
and talk directly to the record? He does so indirectly, by talking to a
stenographer or a wax cylinder; but the elements are all present if he
wishes to have his talk directly produce a typed record. All he needs to do
is to take advantage of existing mechanisms and to alter his language.

At a recent World Fair a machine called a Voder was shown. A girl stroked
its keys and it emitted recognizable speech. No human vocal chords entered
into the procedure at any point; the keys simply combined some electrically
produced vibrations and passed these on to a loud-speaker. In the Bell
Laboratories there is the converse of this machine, called a Vocoder. The
loudspeaker is replaced by a microphone, which picks up sound. Speak to it,
and the corresponding keys move. This may be one element of the postulated
system.

The other element is found in the stenotype, that somewhat disconcerting
device encountered usually at public meetings. A girl strokes its keys
languidly and looks about the room and sometimes at the speaker with a
disquieting gaze. From it emerges a typed strip which records in a
phonetically simplified language a record of what the speaker is supposed to
have said. Later this strip is retyped into ordinary language, for in its
nascent form it is intelligible only to the initiated. Combine these two
elements, let the Vocoder run the stenotype, and the result is a machine
which types when talked to.

Our present languages are not especially adapted to this sort of
mechanization, it is true. It is strange that the inventors of universal
languages have not seized upon the idea of producing one which better fitted
the technique for transmitting and recording speech. Mechanization may yet
force the issue, especially in the scientific field; whereupon scientific
jargon would become still less intelligible to the layman.

One can now picture a future investigator in his laboratory. His hands are
free, and he is not anchored. As he moves about and observes, he photographs
and comments. Time is automatically recorded to tie the two records
together. If he goes into the field, he may be connected by radio to his
recorder. As he ponders over his notes in the evening, he again talks his
comments into the record. His typed record, as well as his photographs, may
both be in miniature, so that he projects them for examination.

Much needs to occur, however, between the collection of data and
observations, the extraction of parallel material from the existing record,
and the final insertion of new material into the general body of the common
record. For mature thought there is no mechanical substitute. But creative
thought and essentially repetitive thought are very different things. For
the latter there are, and may be, powerful mechanical aids.

Adding a column of figures is a repetitive thought process, and it was
long ago properly relegated to the machine. True, the machine is sometimes
controlled by a keyboard, and thought of a sort enters in reading the
figures and poking the corresponding keys, but even this is avoidable.
Machines have been made which will read typed figures by photocells and then
depress the corresponding keys; these are combinations of photocells for
scanning the type, electric circuits for sorting the consequent variations,
and relay circuits for interpreting the result into the action of solenoids
to pull the keys down.

All this complication is needed because of the clumsy way in which we have
learned to write figures. If we recorded them positionally, simply by the
configuration of a set of dots on a card, the automatic reading mechanism
would become comparatively simple. In fact if the dots are holes, we have
the punched-card machine long ago produced by Hollorith for the purposes of
the census, and now used throughout business. Some types of complex
businesses could hardly operate without these machines.

Adding is only one operation. To perform arithmetical computation involves
also subtraction, multiplication, and division, and in addition some method
for temporary storage of results, removal from storage for further
manipulation, and recording of final results by printing. Machines for these
purposes are now of two types: keyboard machines for accounting and the
like, manually controlled for the insertion of data, and usually
automatically controlled as far as the sequence of operations is concerned;
and punched-card machines in which separate operations are usually delegated
to a series of machines, and the cards then transferred bodily from one to
another. Both forms are very useful; but as far as complex computations are
concerned, both are still in embryo.

Rapid electrical counting appeared soon after the physicists found it
desirable to count cosmic rays. For their own purposes the physicists
promptly constructed thermionic-tube equipment capable of counting
electrical impulses at the rate of 100,000 a second. The advanced
arithmetical machines of the future will be electrical in nature, and they
will perform at 100 times present speeds, or more.

Moreover, they will be far more versatile than present commercial
machines, so that they may readily be adapted for a wide variety of
operations. They will be controlled by a control card or film, they will
select their own data and manipulate it in accordance with the instructions
thus inserted, they will perform complex arithmetical computations at
exceedingly high speeds, and they will record results in such form as to be
readily available for distribution or for later further manipulation. Such
machines will have enormous appetites. One of them will take instructions
and data from a whole roomful of girls armed with simple key board punches,
and will deliver sheets of computed results every few minutes. There will
always be plenty of things to compute in the detailed affairs of millions of
people doing complicated things.

4

The repetitive processes of thought are not confined however, to matters
of arithmetic and statistics. In fact, every time one combines and records
facts in accordance with established logical processes, the creative aspect
of thinking is concerned only with the selection of the data and the process
to be employed and the manipulation thereafter is repetitive in nature and
hence a fit matter to be relegated to the machine. Not so much has been done
along these lines, beyond the bounds of arithmetic, as might be done,
primarily because of the economics of the situation. The needs of business
and the extensive market obviously waiting, assured the advent of
mass-produced arithmetical machines just as soon as production methods were
sufficiently advanced.

With machines for advanced analysis no such situation existed; for there
was and is no extensive market; the users of advanced methods of
manipulating data are a very small part of the population. There are,
however, machines for solving differential equations -- and functional and
integral equations, for that matter. There are many special machines, such
as the harmonic synthesizer which predicts the tides. There will be many
more, appearing certainly first in the hands of the scientist and in small
numbers.

If scientific reasoning were limited to the logical processes of
arithmetic, we should not get far in our understanding of the physical
world. One might as well attempt to grasp the game of poker entirely by the
use of the mathematics of probability. The abacus, with its beads strung on
parallel wires, led the Arabs to positional numeration and the concept of
zero many centuries before the rest of the world; and it was a useful tool
-- so useful that it still exists.

It is a far cry from the abacus to the modern keyboard accounting machine.
It will be an equal step to the arithmetical machine of the future. But even
this new machine will not take the scientist where he needs to go. Relief
must be secured from laborious detailed manipulation of higher mathematics
as well, if the users of it are to free their brains for something more than
repetitive detailed transformations in accordance with established rules. A
mathematician is not a man who can readily manipulate figures; often he
cannot. He is not even a man who can readily perform the transformations of
equations by the use of calculus. He is primarily an individual who is
skilled in the use of symbolic logic on a high plane, and especially he is a
man of intuitive judgment in the choice of the manipulative processes he
employs.

All else he should be able to turn over to his mechanism, just as
confidently as he turns over the propelling of his car to the intricate
mechanism under the hood. Only then will mathematics be practically
effective in bringing the growing knowledge of atomistics to the useful
solution of the advanced problems of chemistry, metallurgy, and biology. For
this reason there still come more machines to handle advanced mathematics
for the scientist. Some of them will be sufficiently bizarre to suit the
most fastidious connoisseur of the present artifacts of civilization.

5

The scientist, however, is not the only person who manipulates data and
examines the world about him by the use of logical processes, although he
sometimes preserves this appearance by adopting into the fold anyone who
becomes logical, much in the manner in which a British labor leader is
elevated to knighthood. Whenever logical processes of thought are employed
-- that is, whenever thought for a time runs along an accepted groove --
there is an opportunity for the machine. Formal logic used to be a keen
instrument in the hands of the teacher in his trying of students' souls. It
is readily possible to construct a machine which will manipulate premises in
accordance with formal logic, simply by the clever use of relay circuits.
Put a set of premises into such a device and turn the crank, and it will
readily pass out conclusion after conclusion, all in accordance with logical
law, and with no more slips than would be expected of a keyboard adding
machine.

Logic can become enormously difficult, and it would undoubtedly be well to
produce more assurance in its use. The machines for higher analysis have
usually been equation solvers. Ideas are beginning to appear for equation
transformers, which will rearrange the relationship expressed by an equation
in accordance with strict and rather advanced logic. Progress is inhibited
by the exceedingly crude way in which mathematicians express their
relationships. They employ a symbolism which grew like Topsy and has little
consistency; a strange fact in that most logical field.

A new symbolism, probably positional, must apparently precede the
reduction of mathematical transformations to machine processes. Then, on
beyond the strict logic of the mathematician, lies the application of logic
in everyday affairs. We may some day click off arguments on a machine with
the same assurance that we now enter sales on a cash register. But the
machine of logic will not look like a cash register, even of the streamlined
model.

So much for the manipulation of ideas and their insertion into the record.
Thus far we seem to be worse off than before -- for we can enormously extend
the record; yet even in its present bulk we can hardly consult it. This is a
much larger matter than merely the extraction of data for the purposes of
scientific research; it involves the entire process by which man profits by
his inheritance of acquired knowledge. The prime action of use is selection,
and here we are halting indeed. There may be millions of fine thoughts, and
the account of the experience on which they are based, all encased within
stone walls of acceptable architectural form; but if the scholar can get at
only one a week by diligent search, his syntheses are not likely to keep up
with the current scene.

Selection, in this broad sense, is a stone adze in the hands of a
cabinetmaker. Yet, in a narrow sense and in other areas, something has
already been done mechanically on selection. The personnel officer of a
factory drops a stack of a few thousand employee cards into a selecting
machine, sets a code in accordance with an established convention, and
produces in a short time a list of all employees who live in Trenton and
know Spanish. Even such devices are much too slow when it comes, for
example, to matching a set of fingerprints with one of five million on file.
Selection devices of this sort will soon be speeded up from their present
rate of reviewing data at a few hundred a minute. By the use of photocells
and microfilm they will survey items at the rate of a thousand a second, and
will print out duplicates of those selected.

This process, however, is simple selection: it proceeds by examining in
turn every one of a large set of items, and by picking out those which have
certain specified characteristics. There is another form of selection best
illustrated by the automatic telephone exchange. You dial a number and the
machine selects and connects just one of a million possible stations. It
does not run over them all. It pays attention only to a class given by a
first digit, then only to a subclass of this given by the second digit, and
so on; and thus proceeds rapidly and almost unerringly to the selected
station. It requires a few seconds to make the selection, although the
process could be speeded up if increased speed were economically warranted.
If necessary, it could be made extremely fast by substituting
thermionic-tube switching for mechanical switching, so that the full
selection could be made in one one-hundredth of a second. No one would wish
to spend the money necessary to make this change in the telephone system,
but the general idea is applicable elsewhere.

Take the prosaic problem of the great department store. Every time a
charge sale is made, there are a number of things to be done. The inventory
needs to be revised, the salesman needs to be given credit for the sale, the
general accounts need an entry, and, most important, the customer needs to
be charged. A central records device has been developed in which much of
this work is done conveniently. The salesman places on a stand the
customer's identification card, his own card, and the card taken from the
article sold -- all punched cards. When he pulls a lever, contacts are made
through the holes, machinery at a central point makes the necessary
computations and entries, and the proper receipt is printed for the salesman
to pass to the customer.

But there may be ten thousand charge customers doing business with the
store, and before the full operation can be completed someone has to select
the right card and insert it at the central office. Now rapid selection can
slide just the proper card into position in an instant or two, and return it
afterward. Another difficulty occurs, however. Someone must read a total on
the card, so that the machine can add its computed item to it. Conceivably
the cards might be of the dry photography type I have described. Existing
totals could then be read by photocell, and the new total entered by an
electron beam.

The cards may be in miniature, so that they occupy little space. They must
move quickly. They need not be transferred far, but merely into position so
that the photocell and recorder can operate on them. Positional dots can
enter the data. At the end of the month a machine can readily be made to
read these and to print an ordinary bill. With tube selection, in which no
mechanical parts are involved in the switches, little time need be occupied
in bringing the correct card into use -- a second should suffice for the
entire operation. The whole record on the card may be made by magnetic dots
on a steel sheet if desired, instead of dots to be observed optically,
following the scheme by which Poulsen long ago put speech on a magnetic
wire. This method has the advantage of simplicity and ease of erasure. By
using photography, however one can arrange to project the record in enlarged
form and at a distance by using the process common in television equipment.

One can consider rapid selection of this form, and distant projection for
other purposes. To be able to key one sheet of a million before an operator
in a second or two, with the possibility of then adding notes thereto, is
suggestive in many ways. It might even be of use in libraries, but that is
another story. At any rate, there are now some interesting combinations
possible. One might, for example, speak to a microphone, in the manner
described in connection with the speech controlled typewriter, and thus make
his selections. It would certainly beat the usual file clerk.

6

The real heart of the matter of selection, however, goes deeper than a lag
in the adoption of mechanisms by libraries, or a lack of development of
devices for their use. Our ineptitude in getting at the record is largely
caused by the artificiality of systems of indexing. When data of any sort
are placed in storage, they are filed alphabetically or numerically, and
information is found (when it is) by tracing it down from subclass to
subclass. It can be in only one place, unless duplicates are used; one has
to have rules as to which path will locate it, and the rules are cumbersome.
Having found one item, moreover, one has to emerge from the system and
re-enter on a new path.

The human mind does not work that way. It operates by association. With
one item in its grasp, it snaps instantly to the next that is suggested by
the association of thoughts, in accordance with some intricate web of trails
carried by the cells of the brain. It has other characteristics, of course;
trails that are not frequently followed are prone to fade, items are not
fully permanent, memory is transitory. Yet the speed of action, the
intricacy of trails, the detail of mental pictures, is awe-inspiring beyond
all else in nature.

Man cannot hope fully to duplicate this mental process artificially, but
he certainly ought to be able to learn from it. In minor ways he may even
improve, for his records have relative permanency. The first idea, however,
to be drawn from the analogy concerns selection. Selection by association,
rather than indexing, may yet be mechanized. One cannot hope thus to equal
the speed and flexibility with which the mind follows an associative trail,
but it should be possible to beat the mind decisively in regard to the
permanence and clarity of the items resurrected from storage.

Consider a future device for individual use, which is a sort of mechanized
private file and library. It needs a name, and, to coin one at random,
"memex" will do. A memex is a device in which an individual stores all his
books, records, and communications, and which is mechanized so that it may
be consulted with exceeding speed and flexibility. It is an enlarged
intimate supplement to his memory.

It consists of a desk, and while it can presumably be operated from a
distance, it is primarily the piece of furniture at which he works. On the
top are slanting translucent screens, on which material can be projected for
convenient reading. There is a keyboard, and sets of buttons and levers.
Otherwise it looks like an ordinary desk.

In one end is the stored material. The matter of bulk is well taken care
of by improved microfilm. Only a small part of the interior of the memex is
devoted to storage, the rest to mechanism. Yet if the user inserted 5000
pages of material a day it would take him hundreds of years to fill the
repository, so he can be profligate and enter material freely.

Most of the memex contents are purchased on microfilm ready for insertion.
Books of all sorts, pictures, current periodicals, newspapers, are thus
obtained and dropped into place. Business correspondence takes the same
path. And there is provision for direct entry. On the top of the memex is a
transparent platen. On this are placed longhand notes, photographs,
memoranda, all sorts of things. When one is in place, the depression of a
lever causes it to be photographed onto the next blank space in a section of
the memex film, dry photography being employed.

There is, of course, provision for consultation of the record by the usual
scheme of indexing. If the user wishes to consult a certain book, he taps
its code on the keyboard, and the title page of the book promptly appears
before him, projected onto one of his viewing positions. Frequently-used
codes are mnemonic, so that he seldom consults his code book; but when he
does, a single tap of a key projects it for his use. Moreover, he has
supplemental levers. On deflecting one of these levers to the right he runs
through the book before him, each page in turn being projected at a speed
which just allows a recognizing glance at each. If he deflects it further to
the right, he steps through the book 10 pages at a time; still further at
100 pages at a time. Deflection to the left gives him the same control
backwards.

A special button transfers him immediately to the first page of the index.
Any given book of his library can thus be called up and consulted with far
greater facility than if it were taken from a shelf. As he has several
projection positions, he can leave one item in position while he calls up
another. He can add marginal notes and comments, taking advantage of one
possible type of dry photography, and it could even be arranged so that he
can do this by a stylus scheme, such as is now employed in the telautograph
seen in railroad waiting rooms, just as though he had the physical page
before him.

7

All this is conventional, except for the projection forward of present-day
mechanisms and gadgetry. It affords an immediate step, however, to
associative indexing, the basic idea of which is a provision whereby any
item may be caused at will to select immediately and automatically another.
This is the essential feature of the memex. The process of tying two items
together is the important thing.

When the user is building a trail, he names it, inserts the name in his
code book, and taps it out on his keyboard. Before him are the two items to
be joined, projected onto adjacent viewing positions. At the bottom of each
there are a number of blank code spaces, and a pointer is set to indicate
one of these on each item. The user taps a single key, and the items are
permanently joined. In each code space appears the code word. Out of view,
but also in the code space, is inserted a set of dots for photocell viewing;
and on each item these dots by their positions designate the index number of
the other item.

Thereafter, at any time, when one of these items is in view, the other can
be instantly recalled merely by tapping a button below the corresponding
code space. Moreover, when numerous items have been thus joined together to
form a trail, they can be reviewed in turn, rapidly or slowly, by deflecting
a lever like that used for turning the pages of a book. It is exactly as
though the physical items had been gathered together from widely separated
sources and bound together to form a new book. It is more than this, for any
item can be joined into numerous trails.

The owner of the memex, let us say, is interested in the origin and
properties of the bow and arrow. Specifically he is studying why the short
Turkish bow was apparently superior to the English long bow in the
skirmishes of the Crusades. He has dozens of possibly pertinent books and
articles in his memex. First he runs through an encyclopedia, finds an
interesting but sketchy article, leaves it projected. Next, in a history, he
finds another pertinent item, and ties the two together. Thus he goes,
building a trail of many items. Occasionally he inserts a comment of his
own, either linking it into the main trail or joining it by a side trail to
a particular item. When it becomes evident that the elastic properties of
available materials had a great deal to do with the bow, he branches off on
a side trail which takes him through textbooks on elasticity and tables of
physical constants. He inserts a page of longhand analysis of his own. Thus
he builds a trail of his interest through the maze of materials available to
him.

And his trails do not fade. Several years later, his talk with a friend
turns to the queer ways in which a people resist innovations, even of vital
interest. He has an example, in the fact that the outraged Europeans still
failed to adopt the Turkish bow. In fact he has a trail on it. A touch
brings up the code book. Tapping a few keys projects the head of the trail.
A lever runs through it at will, stopping at interesting items, going off on
side excursions. It is an interesting trail, pertinent to the discussion. So
he sets a reproducer in action, photographs the whole trail out, and passes
it to his friend for insertion in his own memex, there to be linked into the
more general trail.

8

Wholly new forms of encyclopedias will appear, ready made with a mesh of
associative trails running through them, ready to be dropped into the memex
and there amplified. The lawyer has at his touch the associated opinions and
decisions of his whole experience, and of the experience of friends and
authorities. The patent attorney has on call the millions of issued patents,
with familiar trails to every point of his client's interest. The physician,
puzzled by a patient's reactions, strikes the trail established in studying
an earlier similar case, and runs rapidly through analogous case histories,
with side references to the classics for the pertinent anatomy and
histology. The chemist, struggling with the synthesis of an organic
compound, has all the chemical literature before him in his laboratory, with
trails following the analogies of compounds, and side trails to their
physical and chemical behavior.

The historian, with a vast chronological account of a people, parallels it
with a skip trail which stops only on the salient items, and can follow at
any time contemporary trails which lead him all over civilization at a
particular epoch. There is a new profession of trail blazers, those who find
delight in the task of establishing useful trails through the enormous mass
of the common record. The inheritance from the master becomes, not only his
additions to the world's record, but for his disciples the entire
scaffolding by which they were erected.

Thus science may implement the ways in which man produces, stores, and
consults the record of the race. It might be striking to outline the
instrumentalities of the future more spectacularly, rather than to stick
closely to methods and elements now known and undergoing rapid development,
as has been done here. Technical difficulties of all sorts have been
ignored, certainly, but also ignored are means as yet unknown which may come
any day to accelerate technical progress as violently as did the advent of
the thermionic tube. In order that the picture may not be too commonplace,
by reason of sticking to present-day patterns, it may be well to mention one
such possibility, not to prophesy but merely to suggest, for prophecy based
on extension of the known has substance, while prophecy founded on the
unknown is only a doubly involved guess.

All our steps in creating or absorbing material of the record proceed
through one of the senses -- the tactile when we touch keys, the oral when
we speak or listen, the visual when we read. Is it not possible that some
day the path may be established more directly?

We know that when the eye sees, all the consequent information is
transmitted to the brain by means of electrical vibrations in the channel of
the optic nerve. This is an exact analogy with the electrical vibrations
which occur in the cable of a television set: they convey the picture from
the photocells which see it to the radio transmitter from which it is
broadcast. We know further that if we can approach that cable with the
proper instruments, we do not need to touch it; we can pick up those
vibrations by electrical induction and thus discover and reproduce the scene
which is being transmitted, just as a telephone wire may be tapped for its
message.

The impulses which flow in the arm nerves of a typist convey to her
fingers the translated information which reaches her eye or ear, in order
that the fingers may be caused to strike the proper keys. Might not these
currents be intercepted, either in the original form in which information is
conveyed to the brain, or in the marvelously metamorphosed form in which
they then proceed to the hand?

By bone conduction we already introduce sounds: into the nerve channels of
the deaf in order that they may hear. Is it not possible that we may learn
to introduce them without the present cumbersomeness of first transforming
electrical vibrations to mechanical ones, which the human mechanism promptly
transforms back to the electrical form? With a couple of electrodes on the
skull the encephalograph now produces pen-and-ink traces which bear some
relation to the electrical phenomena going on in the brain itself. True, the
record is unintelligible, except as it points out certain gross
misfunctioning of the cerebral mechanism; but who would now place bounds on
where such a thing may lead?

In the outside world, all forms of intelligence whether of sound or sight,
have been reduced to the form of varying currents in an electric circuit in
order that they may be transmitted. Inside the human frame exactly the same
sort of process occurs. Must we always transform to mechanical movements in
order to proceed from one electrical phenomenon to another? It is a
suggestive thought, but it hardly warrants prediction without losing touch
with reality and immediateness.

Presumably man's spirit should be elevated if he can better review his
shady past and analyze more completely and objectively his present problems.
He has built a civilization so complex that he needs to mechanize his
records more fully if he is to push his experiment to its logical conclusion
and not merely become bogged down part way there by overtaxing his limited
memory. His excursions may be more enjoyable if he can reacquire the
privilege of forgetting the manifold things he does not need to have
immediately at hand, with some assurance that he can find them again if they
prove important.

The applications of science have built man a well-supplied house, and are
teaching him to live healthily therein. They have enabled him to throw
masses of people against one another with cruel weapons. They may yet allow
him truly to encompass the great record and to grow in the wisdom of race
experience. He may perish in conflict before he learns to wield that record
for his true good. Yet, in the application of science to the needs and
desires of man, it would seem to be a singularly unfortunate stage at which
to terminate the process, or to lose hope as to the outcome.